Pentaerythritol phosphoric acid ester sensitizers for photographic emulsions



United States Patent Cfifice 3,16,863 PENTAERYTHRETUL PHQSPHGRKC AC1!) ESTER SENSITIZERS FOR PEZQTGGRAEH6 EMULSEONS Herbert Grabhiiler, Cologne-Flittard, Herbert Miiller, Leverknsen, Rolf-Fred Posse, Cologne-Flittard, and Hans Ulrich, Leverlrusen, Germany, assignors to Agfa Aktiengesellschaft, Leverlnisen, Germany, a corporation of Germany No Drawing. Filed June 11, 1963, Ser. No. 286,924 Claims priority, application Germany, luly 21, 1962, A 40,784 9 Claims. (Cl. 96-66) The invention relates to chemical sensitizers for photographic emulsions, to photographic emulsions and developer compositions containing these and to the production of photographic images in the presence of said sensitizers.

In the graphic arts field, particularly for raster photography, more and more films are being used which are onthe market as so-called lithographic or line films and which can be developed to very high gamma values and therefore sharp raster points in developers which contain formaldehyde.

Although the processing of such films in developers containing formaldehyde gives excellent results, it must be carried out with great care. The interval during development in which a sharp raster point is obtained, i.e. the steepest gamma, is only short. It amounts to approximately between /2 and 1 /2 minutes.

It is known to add phosphorylated alkylene oxide derivatives to photographic silver halide emulsions to improve the mechanical properties thereof. However, these compounds are unsuitable for obtaining a high contrast.

It has now been found that the gamma values of photographic emulsions and the period during development in which an extremely high gamma value is obtained can be increased, so that development can be carried out much more effectively and conveniently, if the development is carried out in the presence of spirocyclic phosphoric acid esters which are obtainable by reaction of spirocyclic pentaerythritol-di-(phosphoric acid monohalides), particularly -(monochlorides) of the formula vIn this formula, n has the meaning given above, and the degree of condensation X of the product of esterification may be 1 or more, for instance 1-100, preferably 1-10. L1 the above hypothetical formula, the substituent R may represent H or 3,lh9,853 i atented Feb. 16, l65

7 compounds of the following formula where n and X have the meaning given above:

do not produce extremely high gamma values.

Any silver halide emulsions of the developing-out type which provide a high gamma when developed with developers containing formaldehyde may be used. The silver salts of such emulsions generally consist of silver chloride in a quantity of at least 50 mole percent. However, it is preferred to use emulsions in which the silver salts consist at least of 65 mole percent of silver chloride and accordingly 35 mole percent or less of silver bromide. The emulsions may further contain small amounts of silver iodide, such as 1 to 2 mole percent.

.The quantity of the above phosphoric acid esters to be added to the emulsion depends on the ratio of chloride to bromide in the emulsion, 10 to mg. per mol of silver halide may advantageously be used. The emulsions can in addition be chemically sensitized with salts of noble metals, such as gold salts, with sulfur compounds or with reducing agents. Moreover the emulsions can be optically sensitized with cyanine and merocyanine dyes.

The developers which may be employed in our invention contain as essential components a phenol type de veloper, such as hydroquinone, an alkali,such as an alkali metal carbonate, sodium or potassium carbonate, formaldehyde bisulfite and a small amount of a restrainer, such as alkali metal bromide. If desired the developer can also contain sodium hydroxide, boric acid, a sequesterin g agent. Instead of alkali metal carbonate and formaldehyde bisulfite the developer can contain, 'as a source of formaldehyde, paraformaldehyde, an alkali metal sulfite and a buffering agent, such as alkali metal bisulfite. Such developers are well known in the art and are for instance disclosed in US. Patents 2,184,053, 2,313,523, 2,902,367 and in British Patent 643,411. Such developers may contain for instance per one liter 15-25 grams or" hydroquinone, 30-70 grams of formaldehyde bisulfite, 30-90 grams of sodium carbonate monohydrate, 5-20 grams of boric acid and 1-5 grams of alkali metal bromide or 15-25 grams of hydroquinone, 5-10 grams of paraformaldehyde, 1-5 grams of potassium metabisulfite (cryst), 20-40 grams of anhydrous sodium sulphite, 5-15 grams of boric acid and l-5 grams of alkali metal bromide.

The phosphoric acid esters of the present invention may be added to the above lithographic developers perferably in quantities of 30-300 mg. per liter.

The addition of the phosphoric acid esters of the present invention to the emulsion and/or to the developer causes the gamma value to rise considerably during development, for instance from about 6-8 to above 15. At the same time, the margin of time during development within which sharpness of raster dots may be obtained is increased from about one minute to 3 to 4 minutes. Furthermore, a formaldehyde containing developer having such an addition is less dependent upon temperature. Whereas a developer without this addition reacts to temperature increases of 1 to 2 C. with a marked reduction in the margin of time for development, good results may be obtained with developer temperatures of 15 to 40 C. if these phosphoric acid esters have been added. Owing to the increased time available for processing, the above graphic use.

. O -CH Hi described advantages render the Work much more reliable and more free from disturbance.

The phosphoric acid esters according to the invention are prepared by the usual methods used for esterification, and the degree of condensation of the esters may be infiuenced in the desired direction by varying the reaction time, the reaction temperature and the molar proportions of the reaction components. The condensation may for instance be carried through in a liquid alkaline medium, such as in pyridine or triethylamine or other tertiary amines, at temperatures of about 0 to 80 C., preferably to 50 C.

Individual condensative products will be described below in the following preparation examples.

' COMPOUND I CHg-O 0 /P-Cl O-Cfig CHz-O is deposited in the form of colorless crystals, melting point 243-245 C.

The crystals may be isolated by suction filtration after some of the phosphorus oxychloride has been removed by evaporation in vacuo, and the crystals may then be washed with methylene chloride on the suction filter.

(b) 30 g. of the ester chloride (Ia) described above are added in portions with stirring to a mixture of 37.2 g. octaethyleneglycol and 31.2 g. of pyridine, the temperature gradually rising to 35 C. After 4 hours the mixture is poured on to ice, adjusted to pH 3 with 2 N H 80 treated with saturated sodium chloride solution, and extracted with methylene chloride. After drying with potash, the methylene chloride is evaporated oif completely. 25 g. of a light brown highly viscous oil is obtained, which is diluted with water to a 10% solution for photo- The following theoretical formula is derived from the proportions of the starting materials and the molecular weight of 900 determined by osmosis:

If the reaction time is increased the degree of condensation X increases likewise. Alternatively, if the amount of octaethyleneglycol used for the reaction is increased up to 2 moles there are obtained condensation products in which both end groups are mainly formed by -'-(o cH cH oH- radicals.

COMPOUND H 19.4 g. of tetraethylene glycol, 31.2 g. of pyridine and 30 g. of ester chloride (Ia) are reacted as described above and worked up. 27 g. of a viscous light brown oil are obtained. The color may be removed from the 10% aqueous solution by means of active charcoal and bleaching earth. The ioily liquid presumably consists mainly "of a compound of the following theoretical formula:

The variation of the reaction time and proportion of component has the same eifect as disclosed in connection 'with the prescription for the preparation of Compound I.

d COMPOUND III The compound is prepared by a similar method to that used for compound (lb) by reacting 28.2 g. of hexaethyleneglycol and 31.2 g. of pyridine with 30 g. of ester chloride (Ia). Yield 17 g.

I A possible theoretical formula of the end product would be: 7

COMPOUND W 41.4 g. of nonaethyleneglycol, 31.2 g. of pyridine and 30 g. of ester chloride (Ia) produce 20 g. of a brown syrupy polycondensate which is diluted with water to a 10% solution and purified with active charcoal and bleaching earth. The following theoretical formula may be used to represent the highly viscous polycondensate:

COMPOUND V O O-GH; CHz-O O nli X 7 i o a a... .ofl a. g L o-on, onto .|x 7

The preparation of the spirocyclic carbon compounds .used for comparison in the examples will now be described.

COMPOUND VI CH3 OOH2 OHz-O CH3 (3 o \(]JOOOCH5 C-GH: CHg-O Preparation: From pentaerythritol, pyruvic acid and ethanol (Ber. 61 (1928), page 1856).

COMPOUND VII (VII) CO3 O-CEg CHz-O CH3 5 7 oo o-on -oni)son L \OO2 ont-o ix 16.6 g. of Compound VI and 18.5 g. of ioctaethylene glycol are heated for 2 hours at 150 C. in the presence 'of 0.2 g. of sodium methylate, the ethyl alcohol which is liberated distilling off. There reaction product isdiluted with Water to a 10% solution and neutralized with 1 N hydrochloric acid. Osmotic determination of the molecular weight indicated that the value of X was 2.

Example 1 A gelatine-silver halide emulsion the silver halide of which containing 15 mole percent of AgBr and mole percent of AgCl is Washed and then ripened to'maximurn sensitivity and 4-hydroxy-6-rnethyl-l,3,3a,7-tetrazaindole or other stabilizers and a wetting agent are then added, and the emulsion is poured on to a suitable film base (A). In parallel experiments, the following substances,

used as casting additives, are added to the emulsion per mole of silver halide:

(B) +80 mg; octaethylene glycol (C) +80 mg. Compound VII (D) +80 mg. Compound I All the samples are illuminated in a sensitometer behind a grey step wedge and developedfor 5 minutes at 18 C. in a developer of the following composition:

Example 2 An emulsion acording to Example 1 is divided into two portions. One portion (A) has no additive while the other portion (B) has added to it 80 mg. of Compound II per mole of silver halide. Each portion is then poured on to a film base. The two samples are then illuminated and developed as in Example 1.

Result:

Gamma Fog Emulsion A 7 0. ()5 Emulsion B 0. 05

Example 3 An emulsion according to Example 1 is divided into a portion (A) without additive and a portion (B) with 80 mg. of Compound IH per mole of silver halide as additive, and the portions are poured on to a base and then treated as described under 1.

Result:

Gamma Fog Emulsion A 6 0. 04 Emulsion B 15 0, 04

Exampl e 4 Film strips (Agfa-lith-ortho) illuminated behind a stepped wedge are developed in the developer mentioned in Example 1 for varying time ranging from 1 to 4 minutes, at C. The same film samples are developed in the same developer after the addition of 100 rug/liter of Compound I.

Result:

Gamma without additive 7. 5 15 12 6. 5 5. 5 5 +100 mg. I/l 10 15 15 15 15 15 What we claim is:

1. In a process for the production of photographic images by developing silver hmide emulsion layers in which the silver halide has a silver chloride content of at least 50 mole percent with photographic developer solutions containing formaldehyde, the improvement which comprises carrying out said development in the presence of a condensation product Of a pentaerythritol ester of phosphorochloridic acid and a polyethylene glycol with a degree of polymerization of at least 3.

2. A process as defined in claim 1 in which the condensation pro-duct is the condensation product of one mol of a pentaerythritol ester of phosphorochloridic acid and about 1 to 2 mols of a polyethylene glycol.

3. A process as defined in claim 1 in which the condensation product has the formula wherein R represents a member of the group consisting of hydrogen and radicals having the formula \-o11,-oH,-o

in which n represents an integer of at least 3 and X represents an integer of at least 1.

4. A light-sensitive photographic material comprising a silver halide emulsion layer in which the silver halide has a silver chloride content of at least SO-mcl percent, which contains a condensation product as defined in claim 1.

5. A light-sensitive photographic material comprising a silver halide emulsion layer in which the silver halide has a silver chloride content of at least 50-mol percent, which contains a condensation product as defined in claim 2.

6. A light-sensitive photographic material comprising a silver halide emulsion layer in which the silver halide has a silver chloride content of at least 50-mol percent, which contains a condensation product as defined in claim 3.

7. Photographic developing composition comprising hydroquinone and formaldehyde, which contains in addition a condensation product as defined in claim 1.

8. Photographic developing composition comprising hydroquinone and formaldehyde, which contains in addition a condensation product as defined in claim 2.

9. Photographic developing composition comprising hydroquinone and formaldehyde, which contains in addition a condensation product as defined in claim 3.

References Cited in the file of this patent UNITED STATES PATENTS 2,531,832 Stanton Nov. 28, 1950 2,956,881 Van Lare Oct. 18, 1960 2,961,317 Webster et al. Nov. 22, 1960 2,974,158 Lanham Mar. 7, 1961 3,005,007 Fierce et 'al. Oct. 17, 1961 3,090,799 Wahl et al. May 21, 1963 

1. IN A PROCESS FOR THE PRODUCTION OF PHOTOGRAPHIC IMAGES BY DEVELOPING SILVER HALIDE EMULSION LAYERS IN WHICH THE SILVER HALIDE HAS A SILVER CHLORIDE CONTENT OF AT LEAST 50 MOLE PERCENT WITH PHOTOGRAPHIC DEVELOPER SOLUTIONS CONTAINING FORMALDEHYDE, THE IMPROVEMENT WHICH COMPRISES CARRYING OUT SAID DEVELOPMENT IN THE PRESENCE OF A CONDENSATION PRODUCT OF A PENTAERYTHRITOL ESTER OF PHOSPHOROCHLORIDIC ACID AND A POLETHYLENE GLYCOL WITH A DEGREE OF POLYMERIZATION OF AT LEAST
 3. 